Method and system for detecting abnormality of vehicle constant speed travel control

Abstract

A constant speed travel control system uses a time period Q which is set such that, if a motor of the actuator is not locked but normally rotated, actuator opening becomes almost certainly fully closed within that time period with the result that a first limit switch is made open. If the motor is normal, the processing operation proceeds to a normal constant speed travel control by which an electric current to the motor ceases and "motor open" condition is detected. When no "motor open" state is detected, even after the elapse of the time period Q, under the condition that the vehicle speed is higher than a reference speed, a determination that the motor is in the locked condition is made and the operation proceeds to a speed control cancellation process.

What is claimed is: 
     
       1. An abnormality detecting system for a control mechanism which performs a constant speed travel control, said system comprising: vehicle speed detecting means for detecting a speed of a vehicle;   control means having a driving force controlling mechanism for controlling a driving force of an engine of the vehicle, and a motor for driving the driving force controlling mechanism;   constant speed travel controlling means for, on the basis of a deviation between the speed of the vehicle detected by the vehicle speed detecting means and a target speed, controlling the motor so as to reduce the deviation of the detected speed from the target speed and thereby controlling the driving force of the engine by way of the driving force controlling mechanism;   electric current detecting means for detecting an electric current supplied to the motor;   electric current cutting means for cutting an electric current input to the motor when the driving force controlling mechanism has been controlled to a minimum driving-force state;   excess speed state determining means for determining whether or not the speed of the vehicle detected by the vehicle speed detecting means is higher than a reference speed which is higher than the target speed;   driving force minimization controlling means for, when it is being determined by the excess speed state determining means that the detected speed of the vehicle is higher than the reference speed, rotating the motor and thereby controlling the driving force controlling mechanism to the minimum driving-force state; and   abnormality determining means for determining that the control mechanism is abnormal when the electric current to the motor is being detected by the current detecting means for more than a time period during which it is being continuously determined by the excess speed state determining means that the speed of the vehicle is higher than the reference speed.   
     
     
       2. The abnormality detecting system according to claim 1, wherein: the abnormality determining means determines that a state of rotation of the motor is abnormal.   
     
     
       3. The abnormality detecting system according to claim 1, wherein the electric current cutting means comprises: switching means provided on an electric current flow-in path to the motor for cutting off the electric current flow-in path to the motor when the driving force controlling mechanism has been controlled to the minimum driving-force state. 
     
     
       4. The abnormality detecting system according to claim 1, further comprising: constant speed travel control cancellation means for, when it has been determined by the abnormality determining means that the motor rotation state is abnormal, cancelling the control performed by the constant speed travel controlling means.   
     
     
       5. The abnormality detecting system according to claim 1, further comprising: alarm means for generating an alarm when it has been determined by the abnormality determining means that the motor rotation is abnormal.   
     
     
       6. The abnormality detecting system according to claim 1, further comprising: abnormality storing means for, when it has been determined by the abnormality determining means that the motor rotation is abnormal, storing that a determination that the motor is abnormal has been made.   
     
     
       7. The abnormality detecting system according to claim 1, further comprising: power source cutting means for, when it has been determined by the abnormality determining means that the motor rotation is abnormal, cutting off an electric power supply to the constant speed travel controlling means.   
     
     
       8. The abnormality detecting system according to claim 1, further comprising: power source cutting means for, when it has been determined by the abnormality determining means that the control mechanism is abnormal, cutting off an electric power supply to the constant speed travel controlling means.   
     
     
       9. The abnormality detecting system according to claim 1, further comprising: alarm means for generating an alarm when it has been determined by the abnormality determining means that the control mechanism is abnormal.   
     
     
       10. The abnormality detecting system according to claim 1, further comprising: abnormality storing means for, when it has been determined by the abnormality determining means that the control mechanism is abnormal, storing that a determination that the control mechanism is abnormal has been made.   
     
     
       11. The abnormality detecting system according to claim 1, wherein the excess speed determining means comprises: a vehicle speed sensor;   an input buffer to receive a signal from the vehicle speed sensor; and   a microcomputer to receive the signal from the vehicle speed sensor via the input buffer, the microcomputer including: a program executing within the microcomputer for comparing an actual vehicle speed, indicated by the signal from the vehicle speed sensor, with a reference speed contained within a memory of the microcomputer;   the reference speed being a speed which is unlikely to occur during ordinary constant speed travel control.     
     
     
       12. The abnormality detecting system according to claim 1, wherein the driving force controlling means comprises: a first electric current input path on a normal side of the motor;   a first diode electrically connected to the first electric current input path;   a first limit switch arranged in parallel to the first diode;   a second electric current input path on a reverse side of the motor;   a second diode electrically connected to the second electric current input path; and   a second limit switch arranged in parallel to the second diode.   
     
     
       13. The abnormality detecting system according to claim 1, wherein the constant speed travel controlling means comprises: a set switch;   a resume switch;   a cancellation switch;   a vehicle speed sensor;   a stop lamp switch;   an idle switch;   an input buffer to receive signals from the set switch, the resume switch, the cancellation switch, the vehicle speed sensor, the stop lamp switch, and the idle switch; and   a microcomputer to receive the signals via the input buffer and to output a drive instruction to an actuator driving stage.   
     
     
       14. The abnormality detecting system according to claim 1, wherein the electric current curing means comprises: a limit switch.   
     
     
       15. The abnormality detecting system according to claim 2, further comprising: alarm means for generating an alarm when it has been determined by the abnormality determining means that the state of rotation of the motor is abnormal.   
     
     
       16. The abnormality detecting system according to claim 2, further comprising: abnormality storing means for, when it has been determined by the abnormality determining means that the state of rotation of the motor is abnormal, storing that a determination that the state of rotation of the motor is abnormal has been made.   
     
     
       17. The abnormality detecting system according to claim 2, further comprising: power source cutting means for, when it has been determined by the abnormality determining means that the state of rotation of the motor is abnormal, cutting off an electric power supply to the constant speed travel controlling means.   
     
     
       18. A method for detecting an abnormality in a vehicle speed control mechanism which includes an electric motor and controls the electric motor in a direction to reduce a deviation of an actual vehicle speed from a target vehicle speed, the method comprising steps of: detecting an excess speed condition in which the actual vehicle speed is higher than a reference speed which is higher than the target vehicle speed, the target vehicle speed being a desired vehicle speed which the vehicle speed control mechanism attempts to maintain;   detecting an electric current supplied to the electric motor;   rotating the electric motor in a direction such that the vehicle speed control mechanism is put into a minimum condition for reducing an output power of an engine of the vehicle when the excess speed condition is detected;   cutting off the electric current to the electric motor when the vehicle control mechanism is put into the minimum condition; and   determining an abnormality in the vehicle speed control mechanism when the electric current is detected by the step of detecting an electric current while the excess speed condition is being detected for more than a predetermined time period.   
     
     
       19. The method for detecting the abnormality in the vehicle speed control mechanism according to claim 18, further comprising a step of: canceling control of the vehicle speed control mechanism when the step of determining the abnormality in the vehicle speed control mechanism determines the abnormality.   
     
     
       20. The method for detecting the abnormality in the vehicle speed control mechanism according to claim 18 further comprising a step of: generating an alarm when the step of determining the abnormality in the vehicle speed control mechanism determines the abnormality.   
     
     
       21. The method for detecting the abnormality in the vehicle speed control mechanism according to claim 18, further comprising a step of: storing a determination that the electric motor is abnormal when the step of determining the abnormality in the vehicle speed control mechanism determines the abnormality.   
     
     
       22. The method for detecting the abnormality in the vehicle speed control mechanism according to claim 18, further comprising a step of: cutting off an electric power supply to the vehicle speed control mechanism when the step of determining the abnormality in the vehicle speed control mechanism determines the abnormality.   
     
     
       23. The method for detecting an abnormality in the vehicle speed control mechanism according to claim 18, wherein: the reference speed is a speed which is unlikely to occur during ordinary constant speed travel control.   
     
     
       24. An abnormality detecting system for a constant speed travel control, comprising: vehicle speed detecting means for detecting a speed of a vehicle;   control mechanism comprising: a driving force controlling mechanism for controlling a driving force of an engine of the vehicle,   a power transmission mechanism enabling a transmission of power to the driving force controlling mechanism, and   a motor for driving the driving force controlling mechanism through the power transmission mechanism;     constant speed travel control means for, upon receipt of a constant speed travel control instruction, making the power transmission mechanism able to transmit power to the driving force controlling mechanism and based on a deviation between the speed of the vehicle detected by the vehicle speed detecting means and a target speed controlling the motor so as to reduce the deviation and thereby controlling the driving force of the engine by way of the power transmission mechanism and the driving force controlling mechanism;   electric current detecting means for detecting an electric current supplied to the motor;   electric current cutting means for cutting off electric current input to the motor when the power transmission mechanism has been controlled to a minimum power transmission state;   excess speed state determining means for determining whether or not the speed of the vehicle detected by the vehicle speed detecting means is higher than a reference speed obtained by adding to the target speed a speed substantially the same as a deviation which, during a state of control wherein the speed of the vehicle is controlled to a speed substantially equal to the target speed, is unlikely to occur during an ordinary constant speed travel control;   driving force minimization controlling means for, when it is being determined by the excess speed state determining means that the speed of the vehicle is higher than the reference speed, rotating the motor and thereby controlling the power transmission mechanism to the minimum power-transmission state; and   abnormality determining means for determining that the control mechanism is abnormal when electric current is being detected by the electric current detecting means when it is being determined by the excess speed state determining means that a state wherein the speed of the vehicle is higher than the reference speed continues for a prescribed time period, the prescribed time period corresponding to a time period required until the power transmission mechanism is controlled by the driving force minimization controlling means to the minimum power-transmission state.